Electrically conductive fabrics have been widely used in various electronic apparatus to prevent leakage of electromagnetic waves from the apparatus. Among them is fabric of synthetic fiber, made of polymer material such as polyester or nylon, with a metal coating formed on its surface, which is characterized by its two combined characteristics—flexibility from its fiber component and EMI shielding performance from its metal component—finding wide application in the field of gaskets and tapes to be built into electronic apparatus.
The recent development of electronic apparatus reduced in size and increased in frequency has required the development of electrically conductive materials, such as EMI shielding and grounding materials, smaller in thickness and more effective especially in a high frequency region. It is known that metal foil and polymer film coated with metal by deposition or spattering meet these requirements. Such materials, however, have the disadvantages of being lacking in durability, flexibility and softness, which are properties required for their use as EMI shielding and other electrically conductive materials.
JP64-30899A discloses a non-woven fabric for use as an EMI shielding sheet material obtained by bonding a metal plated fiber with a flat cross-section and a thermally melting binder fiber together by melting of said binder fiber. However, this non-woven fabric bases its improved shielding performance on the thermal compression binding of the thermally melting binder fiber to the metal plated fiber, which adversely affects its flexibility and also requires extra steps making its manufacture expensive.
JP8-291432A discloses a flexible woven fabric effective in shielding EMi obtained from a metal monofilament with a flat non-round section spirally wound onto a core yarn composed of 10 or more fibers. This fabric, however, has the disadvantage of requiring an increased amount of the metal monofilament to obtain a satisfactory EMI shielding effect, which, in turn, adversely influences its flexibility, as well as its cost performance.